In the past, wireless communication was used mainly for speech transmission. Various new services have extended the usability of commercial radio systems, such as cellular radio systems, to a new level. The transmission bandwidth of radio systems has increased and services requiring high bandwidth have been introduced. An example of such a service is video transmission.
In addition, new wireless solutions with different characteristics have been presented. Wireless Local Area Network (WLAN) offers high bandwidth. Low power radio frequency (LPRF) connections, such as Bluetooth, offer short range radio based communications with relatively low power consumption. Also the cellular radio systems offer various alternatives for communication.
An important parameter in the design of mobile systems and devices is power consumption. Mobile devices are usually battery or accumulator based and low power consumption increases the usability of these devices. The combination of high data rate transmission and long battery life is still a difficult problem in mobile communications. This applies especially to systems where a large amount of data needs to be transmitted occasionally and at the same time long operating times are required because of the battery based operation.
In prior art, when a high data rate connection is used and there is a pause in the communication, the connection may enter a sleep mode. In sleep mode, the power consumption is smaller than in active mode, which is used in data transmission. However, the power consumption in sleep mode may still be relatively large.